The mechanical properties of carbon nanotubes (CNTs) are discussed, highlighting their high strength, flexibility, and resilience. Experimental results using high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) confirm theoretical predictions that CNTs have exceptional mechanical properties. The paper reviews recent theoretical and experimental findings, emphasizing the relationship between structural order and mechanical properties. It also discusses the challenges in developing CNT-based composites, particularly in achieving efficient load transfer. The mechanical properties of CNTs are strongly dependent on their structure, influenced by the anisotropy of graphite. Three types of CNTs were studied: single-wall nanotube bundles, arc-grown multi-wall nanotubes, and catalytic multi-wall nanotubes. The Young's modulus of a material is crucial for its use in structural applications, as it relates to the cohesion and chemical bonding of atoms. For CNTs, the Young's modulus is related to the sp² bond strength and should match that of a graphene sheet when the diameter is not too small. Theoretical predictions show that the Young's modulus varies with the nanotube diameter and helicity, but only small corrections to the 1/R² behavior are expected. Experimental results indicate that the Young's modulus of CNTs may be higher than that of graphite. The first measurement of the Young's modulus of multi-walled nanotubes was conducted by Treacy and co-workers, showing a trend of higher moduli with smaller diameters. The measurement of single-walled nanotubes at room temperature yielded an average modulus of 1.3 TPa, but uncertainties in temperature and length measurements affected the results. The paper concludes that further research is needed to fully understand the mechanical properties of CNTs and their potential in composite materials.The mechanical properties of carbon nanotubes (CNTs) are discussed, highlighting their high strength, flexibility, and resilience. Experimental results using high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) confirm theoretical predictions that CNTs have exceptional mechanical properties. The paper reviews recent theoretical and experimental findings, emphasizing the relationship between structural order and mechanical properties. It also discusses the challenges in developing CNT-based composites, particularly in achieving efficient load transfer. The mechanical properties of CNTs are strongly dependent on their structure, influenced by the anisotropy of graphite. Three types of CNTs were studied: single-wall nanotube bundles, arc-grown multi-wall nanotubes, and catalytic multi-wall nanotubes. The Young's modulus of a material is crucial for its use in structural applications, as it relates to the cohesion and chemical bonding of atoms. For CNTs, the Young's modulus is related to the sp² bond strength and should match that of a graphene sheet when the diameter is not too small. Theoretical predictions show that the Young's modulus varies with the nanotube diameter and helicity, but only small corrections to the 1/R² behavior are expected. Experimental results indicate that the Young's modulus of CNTs may be higher than that of graphite. The first measurement of the Young's modulus of multi-walled nanotubes was conducted by Treacy and co-workers, showing a trend of higher moduli with smaller diameters. The measurement of single-walled nanotubes at room temperature yielded an average modulus of 1.3 TPa, but uncertainties in temperature and length measurements affected the results. The paper concludes that further research is needed to fully understand the mechanical properties of CNTs and their potential in composite materials.